I do an interval run once a week. The run is 3 miles long and incorporates 8-10 100m sprints. I have been doing this run for the 5+ years that I have been on a paleo style diet. Without intervals I can run 10 miles easily. I also walk for 45 minutes 4 days a week. I do body weight training twice a week and play basketball once a week. The first 2-3 years felt amazing. But the last couple years were very difficult and I felt progressively more fatigued, slower and I would end up with achy legs at night time, and super cold hands. I was never VLC and typically would hover around 125-150g of carbs per day. This year I tweaked my diet and added in more carbs from fruits and having one day of a refeed. Daily I am around 200g of carbs and on reefed days I am over 300g+. My runs are much stronger again and I have way more energy without anymore aches. This is what works best for me since I like being active and enjoy playing sports and being outdoors doing stuff. If the weather is bad and I am working inside all day long my overall carb intake is much lower.
On a side note, before I started upping the carbs I tried to just increase my calories from protein and fats. That went horribly for me. I felt nauseated all the time when I tried to up calories this way instead of proportionately adding in some dietary carbohydrates.
"If man made it, don't eat it" - Jack Lallane
People say I am on a "crazy" diet. What is so crazy about eating veggies, fruits, seafood and organ meats? Just because I don't eat whole wheat and processed food doesn't make my diet "crazy". Maybe everyone else with a SAD are the "crazy" ones for putting that junk in their system.